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Trees: Planting to Replace

Eric Berg

      Arbor Day is fast approaching and in communities all around the state elected officials, community leaders and individuals young and old will gather together, typically in a park, and embrace the act of planting a tree. Typically a proclamation is read, some observations are made and quotes are shared, such as “The best time to plan a tree was 20 years ago. The second best time is now.” This rings true to the planting needs and opportunities in most Nebraska communities.
      Nebraska has seen significant tree loss over the last few years and emerald ash borer (EAB) and other pests, diseases and severe weather will result in even more dramatic loss in coming years. Landowners are accustomed to planting trees in empty spaces but one of the things I recommend is anticipatory planting—planting a tree years, or even decades, before the anticipated removal of an aging or disease-prone specimen.
      If you have a large silver maple or linden in your yard, for example, it may well have a foreseeable and limited lifespan. These and other species are not tolerant of extreme weather and they’re prone to limb breakage from ice, snow and wind events. Or consider all the ash species in our landscapes. Based on an urban plot analysis completed in 2011 by the United States Forest Service and the Nebraska Forest Service, Lincoln has approximately 1,511,000 trees within the city limits. Of this total tree population, ash represents approximately 7.2 percent, which equates to more than 108,000 trees planted along our streets, parks and landscapes that could be lost to EAB.
      So yes, the time to plant is now. But planting close to trees can be challenging. The new tree needs ample root space, has to avoid above and below ground utilities and has to survive with limited sunlight in the shade cast by existing trees. Any new tree may have to tolerate lower levels of light, which will limit species selection and placement and most large-maturing species, including my favorites—the oaks, need six or more hours of direct sunlight daily during the growing season.
      The best place to “replacement plant” is at or near the tree canopy edge east, south or west (north placement will probably be too shady) of the tree you are replacing. In my own home landscape, a large mature green ash planted along the street right-of-way created an opportunity to plant a large-maturing bur oak approximately 20 feet south of it. While slightly in the shadow of the ash, the oak still receives plenty of direct sunlight and when the ash tree declines to EAB, as expected, this oak will be well on its way to fill in the gap and provide on-going generational benefits for our family and for those who might enjoy this landscape well after we are gone. 
      The potential species list for ash alternatives and replacements is a virtual who’s who for diversity and dependability. Some of my favorites for eastern Nebraska include: Kentucky coffee tree, ginkgo, northern catalpa, Osage orange, hickory and many of the oaks such as bur, white, shingle, chestnut and Shumard, to name but a few. On a side note, many of these species, and particularly catalpa, ginkgo and Kentucky coffeetree, are not impressive in a nursery setting. But given time and room to grow, they’ll reward you in the end.
      You can find guidelines for successful planting from ReTree Nebraska and our friends at the Nebraska Statewide Arboretum by visiting retreenebraska.unl.edu and arboretum.unl.edu. So consider your landscape, anticipate any trees you might lose and plant accordingly. Happy Arbor Day!